I've been using my Webber smoker for about a year and a half. On my latest smoke I've noticed a 30 degree temp difference between the probe inserted at the side port and the one at the top rack. The gauge in the lid reads close to the temp at the side port. The temp on the top rack is 30 degrees warmer. I've moved the side port probe to the top rack and it agrees with the probe that is next to it.

I've never used multiple probes before so I'm wondering where do I get an accurate temp reading for whats going on inside the smoker. I know the gauge on the lid isn't as accurate as the other probe but can it be 30 degrees off?

Everything I've smoked has come out fine but now I'm not sure on what temps I've been smoking at in the past.

Currently the upper rack probe reads 280 the side port probe reads 150 and the lid gauge reads 145.

Are you using the same temp probe for the different readings? That could be the issue. Also have you checked the accuracy of the temp probe (boiling water and ice water are the standard measures)?

from 145/150 to 280 is a HUGE difference. Something is amiss in one of the temp gauges. Also since it would violate all laws of thermal dynamics in physics to get a pork butt to 192 internal if the pit temp was only 145/150*, I suspect your probe that is showing 145/150 is the culprit. Check it, but don't toss it out as a lot of temp probes can be recalibrated (but not all).

Also if it's a digital model make sure it's not set for centigrade as 145*C is 293*F which is close to your dome temp (a 13 degree difference would be acceptable, also if you are reading the airflow up the outer edge of a WSM it's going to be a little higher anyway due to the way a WSM works if you have the water pan or a flower pot base, etc... installed.

The 145 and 150 temp were a miss type on my part they were reading 245 and 250. I did have water in the bowl just below the side port probe so that might explain the difference from the probe on the upper rack.

The butt took 16 hours to reach 202 degrees. And turned out very well.

I'll do the water tests on all the units to be sure they are reading accurately.